Is there a way to procedurally scatter objects on the ground of my scene?
Placing Objects Randomly on the Ground with a Hair Particle System

Using a Hair Particle system is a very easy way to have objects scattered randomly on your ground plane. This can be very useful for creating litter in cities, rocks &amp; sticks in woods, trees in forests, weeds in abandoned lots, etc:

 



Step #1: Create your Objects


Add to your scene one of each type of object you want to have scattered on the ground. In this example, I'm using 3 objects:


Each object's Origin Point is the point where the object will touch the ground plane. So, make sure to place the Origin Point accordingly. In this example, we'll move the Origin Point of each object to the mesh's bottom-most point:
Select an object > Edit mode (TAB) > select all (A) > move the object up until it's Origin is at the base of the object:  


Now make all your objects a Group by selecting them all and pressing CTRLG
Then name your group something like "Object Group" in the Tools panel (T)


Now rotate all the objects 90 degrees on the Y axis. This is very important because in hair particle systems, particles use the global +X axis as "up" for orienting the particle (or object, as in the case here):
Object Mode > select object > R > Y > 90  


You can now move them off to the side or to a different layer -- just don't rotate them.




Step #2: Make Your Particle System


Add a Hair particle system to your ground plane:
Select ground plane > Object Properties window > Particle System tab > click New > set Type to Hair  


For the particle system, make the following settings:


Enable Advanced

In the Render section, select Group, and set Dupli Group to your object group, and enable Rotation

Enable the Rotation section, set Initial Orientation to Normal, and the (Rotation) Random to 1

In the Physics section, adjust the Size of your objects, and if you want some of the objects to be random sizes then adjust Random Size

Adjust the Number of objects in the Emission section



The result is a scattering of your objects over the ground: